Arc lamp



June 6, 1950 E, G T ER 2,510,102

ARC LAMP Filed Sept. 11, 1946 I 2 Sheets-Sheet 1 FigJ Fig.4

mm/min. A Ls v E. GRETENER June 6, 1950 ARC LAMP 2 Sheets-Sheet 2 Filed Sept. 11, 19

I Fig. 3

discas Patented June 6, 1950 ABC LAMP Edgar Gretener, Zurich, Switzerland Application September 11,

, In Switzerland September 11, 1945 9 Claims. (01. 314-28) In known are lamps the position of the electrodes is not fixed in space. For example, in the usual high intensity lamp, the feed of the positive carbon is regulated by the aid of a thermostat. The feed of the negative electrode is regulated in such manner that the arc current remains constant. When the arc current is a little too high, the negative feed is reduced and vice versa. with this construction when the thermostat fails to function or the positive drive jams, the positive carbon burns back against its holder, the negative carbon automatically continues to feed and both carbons move towards the positive holder and endanger it. In this case a second thermostat is necessary to operate a protective cut out of the arc, when the positive electrode burns too far back.

The new lamp system has one electrode, preferably the negative, fixed in space which offers very important advantages with regard to the regulation, ignition and safe operation of the lamp.

In contrast to the rod electrodes commonly used, according to the invention the negative electrode consists of a disc, the moving edge of which faces the positive crater so that the arc is iormed between the positive crater and the disc edge. While the lamp is in operation the disc is rotated continuously. By using a suitably sized the negative electrode a very small radial burning rate is obtained, so that in general, the lamp functions correctly for a long time without any regulation of the negative electrode. Generally it is only necessary to feed the disc toward the positive electrode a little by hand from time to time.

For completely automatic lamps, the negative disc electrode is automatically fed or moved bodily toward the positive electrode to correct for the corresponding reduction of its diameter. A feeler continuously .ascertains the disc diameter and regulates the feed so that the point of attachment of the arc (negative spot) is always maintained in the same position in space.

The accompanying drawings serve to explain the invention and illustrate one constructional .example of the latter. They are not intended to be limiting. In the drawings:

Fig. 1 shows diagrammatically the principle of the ilxed position of the negative spot of the arc; Figs. 2 and 3 show in elevation and top view respectively with parts illustrated in section a constructional example of the lamp;

Pig. 4 is a diagram illustrating the relation- 1948, Serial No. 696,120

ship between the arc length and the burning of the positive carbon; v

Fig. 5 shows the wiring diagram of a protecting device.

Referring now to Fig. 1:

At a time t1 the negative disc has a radius 11 and at a time t: it has burnt away to radius r2. Therefore, to keep the negative spot K in a fixed position, the disc must be advanced by the amount 11-1: in the time t2t1 in small increments. lhe correct position of the disc axis is defined automatically by the disc radius at that time, and this is determined by the movement of the feeler A.

In the construction illustrated in Figs. 2 and 3 the principle of the fixed position of the negative spot is realized in a simple and practical manner by the following means: A feeler roller 2 is urged by the action of a spring 3 against the negative disc electrode l. The feeler 2 is connected by means of a rod 6 and springs 4 and 5 with a toothed rack 1. The latter is in mesh with a toothed wheel 8 which in its turn meshes with a toothed rack 9 on which the disc carrying pedestal ill of the lamp is slidably mounted on a guide box II. If in the course of the operation of the lamp the diameter of the disc is reduced the feeler 2 moves upward to remain in contact with the disc and the toothed rack 1 through the intermediary action of the wheel 8 and the toothed rack 9 causes a displacement movement of the pedestal l0 and thereby of. the disc I towards the positive electrode by the amount by which the disc has worn away so that the negative spot I! of the arc remains stationary in its fixed position in space, irrespective of the variations of the diameter of the disc I.

Any actual movement of the are spot due to adjustment at any one instant is limited to a maximum of a fraction of millimeter as the adjustment is substantially continuous. It follows that spot I! will not move from the focal point of reflector 40 more than this amount.

Preferably the feeler is constructed as a revolving roller 2 rotating the disc I by frictional contact and driven by a cord drive ll from an electric motor i3 provided with a suitable reduction gear.

In case the disc electrode does not burn away perfectly uniformly on its circumference and is no longer round it is of advantage to provide for an intermittent feed of the disc so that during the time in which the feed is cut out the deviations from the round may compensate themselves.

I he means for this intermittent feed are according to Fig. 2 the springs 6 and 5, a braking bar 15 cooperating with the guide box Ii and a braking magnet 56. When the latter is energized it presses the braking bar I 5 against the guide box Ii and holds the pedestal It in its fixed position. In case the diameter of the disc decreases during this period in which the feed movement of the pedestal I is blocked an increasing gap between feeler and disc would be formed. This is prevented by the tension spring constituting an elastic member interposed between the feeler and the toothed rack i. The spring power of the compression spring 4 must be greater than that of the tension spring b.

It on the other hand a protuberance is acting on the feeler the latter can move in the downward direction as the precompressed spr 6 permits a movement of the feeler relatively to the toothed rack l held in a fixed position dur= ing that time. c

When the magnet it is deenergized and the pedestal It is released from the locking action of braking bar it on guide box it by clearance W, the tension spring 5 causes a pull on the toothed rack i until it contacts with an abutment face it whereupon the feed movement oi the pedestal ill and thereby of the disc occurs again in the desired manner.

In so far as the consumption of the positive carbon is a constant function of the arc current, with the negative are spot in a fixed position in space, it follows that there is effectively a similarly fixed position of the positive carbon when the latter is fed at a constant speed. The current is a definite function of the arc length and the consumption of the positive carbon is a definite function of the current so that a definite relation exists between the length i orthe arc and the consumption of the positive carbon in de= pendency upon the speed of the feed. The diagram in Fig. 4 illustrates these relations. To obtain a length of the arc of 1s millimetres a feed 01' v millimetres per minute of the positive carbon is necessary. The arc length remains automatically constant as long as the consumption A and the feed speed 0 are unchanged.

In Fig. 2 the constant speed of the positive carbon is obtained by means of a motor l9 running at constant speed and causing through the intermediary of a suitable reduction gear 20, a shaft 2| and a feed wheel 22 a displacement of the positive carbon 23 towards the right, i. e. towards the disc I at a constant speed.

Particular advantages are obtained by using a negative disc in the high intensity lamps with air stream concentration of the arc and high current loading (anode vapour lamp) with coaxial carbons. For projection purposes and searchlights with circular beam cross section, a short arc length is aimed at, in order to attain the desired object: maximum concentration by the use of minimum electrical energy. Using normal negative carbons in this short arc length lamp, particular obstacles are encountered through the condensation of the positive vapour on the tip of the negative carbon, forming a carbide bead or even an additional mushroom-like growth, which after a short time prevents satisfactory burning of the lamp. This effect can be reduced only by suflicient air supply around the tip of the negative electrode, and this is usually accomplished by increasing the arc length.

By using the revolving negative disc the deposit on the negative spot is continuously carried out 0! the arc, where it burns in the fresh 'sion of the positive carbon the carbon through an annular gap between the holding means and the carbon.

The provision of a coaxial magnetic field on the positive side provides a quieter burning of the are as the electrodynamic forces cause a movement of the electrons in annular or helical paths around the axis of the arc whereby a very effective stabilizing of the arc occurs. As is shown in Fig. 2 that field is produced, for example, by means of two windings of a coil 28 arranged concentrically of the axis of the are around the holding means 24 and through which the arc current flows to the contact arrangement re.

A further advantage of the disc electrode with the fixed position of the negative are spot is the practicability of simple, precise and absolutely safe ignition of the arc. To that end, as is shown in Fig. 2, the disc is not mounted in the pedestai ill but in a disc carrier 32 fulcrumed at 33. When the current is interrupted the disc-carrier 32 rotates about pivot 33 under the influence of the spring 33 and causes the disc [I to contact the positive carbon 23. The abutment 35 limits the movement of the disc towards the positive carbon, so that no ignition occurs if the latter recedes too much or is missing. The abutment 35 permits sufiicient movement of the disc i that the left part of the disc is slightly beyond the position of the crater.

When the lamp is switched on the ignition magnet 36 is energized as the current to the disc passes the coil 3'! of the ignition magnet. The force of the magnet overcomes the power of the spring 34 so that the lower part of the disc-carrier is attracted by the magnet, whereupon the disc moves towards th right until the carrier rests on the abutment 38 which defines the position of the negative are spot during the working condition of the lamp. The movement of the disc towards the right automatically causes the ignition'oi the are. As long as the current flows the disc will be maintained in the described position. When the current is interrupted the magnet is de-energized and the disc is again urged towards the positive crater.

A further advantage of the fixed position of the negative are spot is that a protective switch can be provided to operate at a pre-set minimum current if the positive carbon burns too far back. The failure of the positiv feed increases the arc length whilst the position of the negative elec trode remains fixed. The current drops more and more and thus the positive carbon burns back towards its holder so that with a minimum current relay the lamp can switch itself ofi be; fore the positive carbon holder is damaged. This is particularly important in a high intensity lamp with air stream concentration of the arc and high loading of the positive carbon when the protrui'rom its holder is relatively small.

Fig. 5 shows the wiring arrangement of such a protective device. The ignition of the arc ocnet coil Ii or the switch is energized and the circuit oi the arc is closed at the contact I2, the ignition taking place in the manner above de-- scribed. At the same time the relay It becomes operative and by its contact ll maintains the current supply to coil Ii which holds the switch. closed when the key 50 is released. It the pooltive carbon 23 burns towards the left causing an increase of the length or the arc and a decrease or the arc current, the relay 53 is cut out at a determined lower limit whereupon the circuit of the switch operating coil Ii is opened, the circuit of the are broken at switch 52 and the arc extinguished. The switch 55 under spring action is used for cutting out the lamp at will.

In order to obtain a very high light intensity th cathode disc is preferably placed in a meridianal plane of the lighting system and the lamp is so designed that the shadows caused by the holder or the positive and negative electrodes coincide with the shadow of the disc. These relations are indicated in Fig. 3. In plan view the shadow of the disc is limited by the two straight lines 38. The disc carrier 32 and the. suction system 30 are arranged within the shadow cone. The width of the latter on the reflector Ill in the horizontal meridianal plane is indicated by ll. It is assumed that the light is reflected as parallel beams by the reflector so that in the horizontal, meridlanal plane a shadow band indicated in chain-dotted lines and having the width 4| is formed within which the projection of the carrier-means 24 for the positive electrode is situated.

Obviously grinding means may also be provided to smooth the circumference of the discelectrode and keep it continuously in perfectly round condition.

I claim:

1. In an arc lamp, in combination, a positive electrode, a rotatable disc shaped negative electrode, a pedestal, a disc-carrier pivotally mounted on said pedestal, means for automatically moving said pedestal for feeding said disc towards said positive electrode in dependency on the diameter of said disc so that the negative are spot remains fixed in space, and two abutments provided on said pedestal for limiting the positions of said disc-carrier in its working position and in its position for ignition respectively.

2. In an arc lamp, in combination a, positive carbon electrode, a rotating disk shaped negative electrode, and means adapted to provide an air-current coaxially to the positive carbon for stabilizing the arc and direct it toward a fixed point occupied by the negative are spot.

3. In an arc lamp, in combination, a positive electrode, a rotatable disc-shaped negative electrode, a pedestal, a disc carrier movably mounted on said pedestal, means controlled by the diameter of said disc-shaped electrode and connected to said pedestal for bodily moving said pedestal, said disc-shaped electrode and said carrier automatically so that the negative are spot on said disc-shaped electrode remains fixed in space, spaced abutments on said pedestal arranged to engage and limit the displacement of said disc carrier relative to said pedestal whereby the arc-striking movement of said carrier ismaintained within a fixed maximum and is independent oi the decrease in diameter of said disc-shaped negative electrode through said carrier is bodily movable in response thereto.

4. In an arc lamp, in combination, a positive electrode, a rotable disc-shaped negative electrode, mounting means having a disc carrier movably mounted thereon, means controlled by the diameter of said disc-shaped electrode and connected to said mounting means ior bodily moving said mounting means, said disc-carrier and .said disc-shaped electrode automatically to maintain the negative are spot on said discshaped electrode fixed in space, limiting means arranged to engage and limit the displacement of said disc-carrier relative to said mounting means whereby the arc-striking movement of said carrier is maintained within a, fixed maximum and is independent of the decrease in diameter of said disc-shaped negative electrode.

5. The combination set forth in claim 4, air supplying means cooperating with said positive electrode and arranged to provide a cylinder of air around the arc whereby said are is concentrated into a short highly brilliant light source and uneven deposits on said negative discshaped electrode are eliminated.

6. A high intensity carbon arc of great brilliance comprising an elongate positive carbon electrode, a rotatable disc-shaped negative electrode, mounting means having a disc carrier movably mounted thereon, means controlled by the diameter of said disc-shaped electrode and connected to said mounting means for moving said disc-shaped electrode automatically to maintain the negative are spot on said discshaped electrode fixed relative to said positive electrode and air blast means surrounding said elongate positive electrode and projecting a hollow cylinder of air surrounding and concentrating said are into a short highly brilliant light source and providing an oxidizing atmosphere around the heated portion of said disc-shaped electrode just moved i'romthe position of said negative are spot whereby carbon deposits on said disc-shaped electrode are oxidized.

'7. In a high intensity carbon arc of great brilliance, a positive carbon rod electrode, a rotatable disc-shaped negative electrode, mounting means having said negative electrode mounted thereon, means controlled by the diameter of said disc-shaped electrode and connected to said mounting means for moving said disc-shaped electrode automatically to maintain the negative are spot on said disc-shaped electrode fixed in space and air projecting means surrounding said positive electrode and projecting a hollow column of air enclosing said arc, stabilizing it and constituting oxidizing means acting on the heated portion of said disc-shaped electrode just removed from said negative are spot in the direction of rotation to remove deposits therefrom.

B. A high intensity short carbon arc of great brilliance comprising a positive carbon stick electrode, a rotatable disc-shaped negative electrode, means to rotate said disc-shaped electrode and air flow means encircling said positive electrode and projecting a column of air surrounding 'said are, said column of air providing deposit removing means acting on the periphery of said disc-shaped electrode to remove arc deposits thereon.

9. A device to produce a high intensity short carbon arc of great brilliance comprising a positive carbon stick electrode, a rotatable discshaped negative electrode, conduit means around said positive electrode to supply an air current to enclose and to concentrate the arc between said electrodes into a short highly brilliant light source, drive means to rotate said disc electrode said air current constituting deposit removing means acting on the periphery of said discshaped electrode to remove arc deposits therefrom whereby the length and the uniformity of said arc as a, light source is maintained.

EDGAR GIRE'Im The following references are of record in the file of this patent:

UN STA'I'ES i mite Number 2:1. Mar. 145, 123% Number 

